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Fixes for Linux and POSIX speed interfaces; support "sane" termios systems #24

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c24f68c
linux_termios: clear CIBAUD flags, too
Sep 11, 2025
02caf0c
termios: read output speed, not input speed
Sep 11, 2025
f051e30
termios: check to see if termios speed_t is a direct map to baud
Sep 11, 2025
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56 changes: 55 additions & 1 deletion configure.ac
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Original file line number Diff line number Diff line change
Expand Up @@ -111,6 +111,60 @@ AC_SYS_LARGEFILE
# Define size_t if not defined as standard.
AC_TYPE_SIZE_T

# Check to see if the baud rates in termios.h seem sane.
AC_CACHE_CHECK([if <termios.h> is sane], [sp_cv_termios_sane], [
AC_COMPILE_IFELSE([AC_LANG_SOURCE([[
#include <termios.h>
#if (!defined(B0) || B0 == 0) \
&& (!defined(B50) || B50 == 50) \
&& (!defined(B75) || B75 == 75) \
&& (!defined(B110) || B110 == 110) \
&& (!defined(B134) || B134 == 134) \
&& (!defined(B150) || B150 == 150) \
&& (!defined(B200) || B200 == 200) \
&& (!defined(B300) || B300 == 300) \
&& (!defined(B600) || B600 == 600) \
&& (!defined(B1200) || B1200 == 1200) \
&& (!defined(B1800) || B1800 == 1800) \
&& (!defined(B2400) || B2400 == 2400) \
&& (!defined(B4800) || B4800 == 4800) \
&& (!defined(B7200) || B7200 == 7200) \
&& (!defined(B9600) || B9600 == 9600) \
&& (!defined(B14400) || B14400 == 14400) \
&& (!defined(B19200) || B19200 == 19200) \
&& (!defined(B28800) || B28800 == 28800) \
&& (!defined(B33600) || B33600 == 33600) \
&& (!defined(B38400) || B38400 == 38400) \
&& (!defined(B57600) || B57600 == 57600) \
&& (!defined(B76800) || B76800 == 76800) \
&& (!defined(B115200) || B115200 == 115200) \
&& (!defined(B153600) || B153600 == 153600) \
&& (!defined(B230400) || B230400 == 230400) \
&& (!defined(B307200) || B307200 == 307200) \
&& (!defined(B460800) || B460800 == 460800) \
&& (!defined(B500000) || B500000 == 500000) \
&& (!defined(B576000) || B576000 == 576000) \
&& (!defined(B614400) || B614400 == 614400) \
&& (!defined(B921600) || B921600 == 921600) \
&& (!defined(B1000000) || B1000000 == 1000000) \
&& (!defined(B1152000) || B1152000 == 1152000) \
&& (!defined(B1500000) || B1500000 == 1500000) \
&& (!defined(B2000000) || B2000000 == 2000000) \
&& (!defined(B2500000) || B2500000 == 2500000) \
&& (!defined(B3000000) || B3000000 == 3000000) \
&& (!defined(B3500000) || B3500000 == 3500000) \
&& (!defined(B4000000) || B4000000 == 4000000) \
&& (!defined(B5000000) || B5000000 == 5000000) \
&& (!defined(B10000000) || B10000000 == 10000000)
# define TERMIOS_SPEED_T_SANE 1
#else
# error "<termios.h> uses stupid constants"
#endif
]])], [sp_cv_termios_sane=yes], [sp_cv_termios_sane=no])])

AS_IF([test x$sp_cv_termios_sane = xyes],
[AC_DEFINE(HAVE_SANE_TERMIOS, 1, [<termios.h> speeds are sane])],
[
# Check for specific termios structures.
AC_CHECK_TYPES([struct termios2],,,
[[#include <linux/termios.h>]])
Expand All @@ -121,7 +175,7 @@ AC_CHECK_MEMBERS([struct termios.c_ispeed, struct termios.c_ospeed,
# Check for the BOTHER definition, needed for setting arbitrary baud rates.
# We can't just #ifdef BOTHER in the code, because of the separation between
# code using libc headers and code using kernel termios.h headers.
AC_CHECK_DECLS([BOTHER],,, [[#include <linux/termios.h>]])
AC_CHECK_DECLS([BOTHER],,, [[#include <linux/termios.h>]])])

# Check for serial_struct.
AC_CHECK_TYPES([struct serial_struct],,, [[#include <linux/serial.h>]])
Expand Down
7 changes: 5 additions & 2 deletions libserialport_internal.h
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Original file line number Diff line number Diff line change
Expand Up @@ -130,8 +130,11 @@
#endif

/* Non-standard baudrates are not available everywhere. */
#if (defined(HAVE_TERMIOS_SPEED) || defined(HAVE_TERMIOS2_SPEED)) && HAVE_DECL_BOTHER
#define USE_TERMIOS_SPEED
#ifdef HAVE_SANE_TERMIOS
/* Directly supported by termios */
# undef USE_TERMIOS_SPEED
#elif (defined(HAVE_TERMIOS_SPEED) || defined(HAVE_TERMIOS2_SPEED)) && HAVE_DECL_BOTHER
# define USE_TERMIOS_SPEED
#endif

struct sp_port {
Expand Down
14 changes: 9 additions & 5 deletions linux_termios.c
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Original file line number Diff line number Diff line change
Expand Up @@ -18,10 +18,10 @@
*/

/*
* At the time of writing, glibc does not support the Linux kernel interfaces
* for setting non-standard baud rates and flow control. We therefore have to
* prepare the correct ioctls ourselves, for which we need the declarations in
* linux/termios.h.
* glibc before version 2.42 does not support the Linux kernel
* interfaces for setting non-standard baud rates and flow control. We
* therefore have to prepare the correct ioctls ourselves, for which
* we need the declarations in linux/termios.h.
*
* We can't include linux/termios.h in serialport.c however, because its
* contents conflict with the termios.h provided by glibc. So this file exists
Expand All @@ -38,6 +38,8 @@
#include <linux/termios.h>
#include "linux_termios.h"

#ifndef HAVE_SANE_TERMIOS

SP_PRIV unsigned long get_termios_get_ioctl(void)
{
#ifdef HAVE_STRUCT_TERMIOS2
Expand Down Expand Up @@ -86,7 +88,7 @@ SP_PRIV void set_termios_speed(void *data, int speed)
#else
struct termios *term = (struct termios *) data;
#endif
term->c_cflag &= ~CBAUD;
term->c_cflag &= ~(CBAUD | CIBAUD);
term->c_cflag |= BOTHER;
term->c_ispeed = term->c_ospeed = speed;
}
Expand Down Expand Up @@ -127,3 +129,5 @@ SP_PRIV void set_termiox_flow(void *data, int rts, int cts, int dtr, int dsr)
termx->x_cflag |= DSRXON;
}
#endif

#endif
23 changes: 20 additions & 3 deletions serialport.c
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Original file line number Diff line number Diff line change
Expand Up @@ -23,6 +23,7 @@

#include "libserialport_internal.h"

#ifndef HAVE_SANE_TERMIOS
static const struct std_baudrate std_baudrates[] = {
#ifdef _WIN32
/*
Expand All @@ -42,8 +43,8 @@ static const struct std_baudrate std_baudrates[] = {
#endif
#endif
};

#define NUM_STD_BAUDRATES ARRAY_SIZE(std_baudrates)
#endif

void (*sp_debug_handler)(const char *format, ...) = sp_default_debug_handler;

Expand Down Expand Up @@ -1692,7 +1693,9 @@ static enum sp_return set_flow(int fd, struct port_data *data)
static enum sp_return get_config(struct sp_port *port, struct port_data *data,
struct sp_port_config *config)
{
#ifndef HAVE_SANE_TERMIOS
unsigned int i;
#endif

TRACE("%p, %p, %p", port, data, config);

Expand Down Expand Up @@ -1811,22 +1814,26 @@ static enum sp_return get_config(struct sp_port *port, struct port_data *data,
data->termiox_supported = 0;
#endif

#ifdef HAVE_SANE_TERMIOS
config->baudrate = cfgetospeed(&data->term);
#else
for (i = 0; i < NUM_STD_BAUDRATES; i++) {
if (cfgetispeed(&data->term) == std_baudrates[i].index) {
if (cfgetospeed(&data->term) == std_baudrates[i].index) {
config->baudrate = std_baudrates[i].value;
break;
}
}

if (i == NUM_STD_BAUDRATES) {
#ifdef __APPLE__
config->baudrate = (int)data->term.c_ispeed;
config->baudrate = (int)data->term.c_ospeed;
#elif defined(USE_TERMIOS_SPEED)
TRY(get_baudrate(port->fd, &config->baudrate));
#else
config->baudrate = -1;
#endif
}
#endif

switch (data->term.c_cflag & CSIZE) {
case CS8:
Expand Down Expand Up @@ -1898,7 +1905,10 @@ static enum sp_return get_config(struct sp_port *port, struct port_data *data,
static enum sp_return set_config(struct sp_port *port, struct port_data *data,
const struct sp_port_config *config)
{
#ifndef HAVE_SANE_TERMIOS
unsigned int i;
#endif

#ifdef __APPLE__
BAUD_TYPE baud_nonstd;

Expand Down Expand Up @@ -2064,6 +2074,12 @@ static enum sp_return set_config(struct sp_port *port, struct port_data *data,
int controlbits;

if (config->baudrate >= 0) {
#ifdef HAVE_SANE_TERMIOS
if (cfsetospeed(&data->term, config->baudrate) < 0)
RETURN_FAIL("cfsetospeed() failed");
if (cfsetispeed(&data->term, config->baudrate) < 0)
RETURN_FAIL("cfsetispeed() failed");
#else
for (i = 0; i < NUM_STD_BAUDRATES; i++) {
if (config->baudrate == std_baudrates[i].value) {
if (cfsetospeed(&data->term, std_baudrates[i].index) < 0)
Expand All @@ -2088,6 +2104,7 @@ static enum sp_return set_config(struct sp_port *port, struct port_data *data,
RETURN_ERROR(SP_ERR_SUPP, "Non-standard baudrate not supported");
#endif
}
#endif
}

if (config->bits >= 0) {
Expand Down